Contactless measuring system

ABSTRACT

The invention relates to a contactless measuring system having at least one test probe forming part of a coupling structure for the contactless decoupling of a signal running on a signal waveguide, wherein the signal waveguide is designed as a conductor of the electric circuit on a circuit board and as part of an electric circuit. To this end, at least one contact structure is configured and disposed on the circuit board such that said contact structure is galvanically separated from the signal waveguide, forms part of the coupling structure, is displaced completely within the near field of the signal waveguide, and has at least one contact point, which may be electrically contacted by a contact of the test prod.

The present invention relates to a contactless measuring systemcomprising at least one test probe forming part of a coupling structurefor contactless decoupling of a signal running on a signal waveguide,wherein the signal waveguide is configured as a conductor track and aspart of an electric circuit on a circuit board of the electricalcircuit, according to the preamble of claim 1. The invention alsorelates to a calibration substrate for a contactless measuring systemcomprising at least one test probe forming part of a coupling structurefor contactless decoupling of a signal running on a signal waveguide,wherein at least one calibration element, in particular a short-circuitstandard, an open circuit standard, a resistance standard or a conductorstandard is provided on the calibration substrate, wherein the at leastone calibration element is electrically connected to at least one signalwaveguide, in particular a microstrip transmission line or a coplanarwaveguide, according to the preamble of claim 17.

The determination of scattering parameters of electrical componentsembedded within a complex circuit by means of a contactless vectornetwork analysis is known, for example from T. Zelder, H. Eul,“Contactless network analysis with improved dynamic range usingdiversity calibration”, Proceedings of the 36^(th) European MicrowaveConference, Manchester, UK, pages 478 to 481, September 2006 or T.Zelder, H. Rabe, H. Eul, “Contactless electromagnetic measuring systemusing conventional calibration algorithms to determine scatteringparameters”, Advances in Radio Science—Kleinheubacher Berichte 2006,vol. 5, 2007. Compared with conventional contact-bound network analysismethods, the internal directional couplers of a network analyser arereplaced with contactless near field measuring probes which are directlyconnected to the vectorial measuring points of the analyser. Themeasuring probes are positioned over the signal lines of the objectbeing measured. The probes can act inductively and/or capacitively onthe electromagnetic field of the planar conductor. In order to measurethe scattering parameters, conventional calibration methods are used,such as are used for contact-bound network analysis.

In contactless vector network analysis, for each measuring port of anunknown test object (DUT—Device Under Test), at least one measuringprobe, for example, a conductor loop or two capacitive probes areneeded. It is known from, for example, F. De Groote, J. Verspecht, C.Tsironis, D. Barataud and J. -P. Teyssier, “An improved coupling methodfor time domain load-pull measurements”, European Microwave Conference,vol. 1, pages 4 ff., October 2005, to use contactless conductor loopsmade from coaxial semi-rigid lines. By contrast, it is known from T.Zelder, H. Eul, “Contactless network analysis with improved dynamicrange using diversity calibration”, Proceedings of the 36^(th) EuropeanMicrowave Conference, Manchester, UK, pages 478 to 481, September 2006or T. Zelder, H. Rabe, H. Eul, “Contactless electromagnetic measuringsystem using conventional calibration algorithms to determine scatteringparameters”, Advances in Radio Science—Kleinheubacher Berichte 2006,vol. 5, 2007, to use exclusively capacitive probes in contactlessmeasuring systems. From T. Zelder, I. Rolfes, H. Eul, “Contactlessvector network analysis using diversity calibration with capacitive andinductive coupled probes”, Advances in Radio Science—KleinheubacherBerichte 2006, vol. 5, 2007 and J. Stenarson, K. Yhland, C. Wingqvist,“An in-circuit noncontacting measurement method for S-parameters andpower in planar circuits”, IEEE Transactions on Microwave Theory andTechniques, vol. 49, No. 12, pages 2567 to 2572, December 2001,measuring systems are known which are realised with a combination ofcapacitive and inductive probes.

Although contactless vector network analysis has the potential ofcharacterising components contactlessly, to date no contactlessscattering parameter measurement of HF and microwave components embeddedwithin a circuit has been performed. If measurements are to be madewithin a circuit, the positions of the contactless probes must bechanged during and after the calibration. However, this implies a highlevel of complexity in order to reproduce the test probe positionsduring measurement of the calibration standard and of the test object,since the smallest deviations in the probe positioning lead tosignificant measuring errors.

It is an object of the invention to provide a contactless measuringsystem of the aforementioned type such that expensive and complexpositioning of coupling probes can be dispensed with.

This aim is achieved according to the invention with a contactlessmeasuring system of the aforementioned type having the characterisingfeatures of claim 1 and with a calibration substrate of theaforementioned type having the characterising features of claim 17.Advantageous embodiments of the invention are described in the furtherclaims.

With a contactless measuring system of the aforementioned type, it isprovided according to the invention that at least one contact structureis configured and arranged on the circuit board such that said contactstructure is galvanically separated from the signal waveguide, formspart of the coupling structure, is arranged completely within the nearfield of the signal waveguide and comprises at least one contact pointwhich can be electrically contacted by a contact of a test probe.

This has the advantage that the contact structure and thus the wholecoupling structure has a precisely defined geometrical arrangementrelative to the signal waveguide, wherein manual positioning of thecoupling structure can be dispensed with. Reproducible coupling betweenthe signal waveguide and the coupling structure can be easily achieved.

Suitably, the contact structure is configured as a conductor track onthe circuit board.

Particularly good signal coupling can be achieved in that the contactstructure is configured so that said contact structure can be contactedby a test probe in impedance-controlled manner.

At least one contact structure is configured, for example, as a couplingwaveguide with an inner conductor and an outer conductor or as at leastone contact point or contact surface for a contact of a test probe.

Suitably, the contact structure and/or the signal waveguide isconfigured as printed conductor tracks on the circuit board.

For example, the circuit board is configured as a printed circuit board(PCB) or a wafer.

Optimal directional damping or a port with wide-band insulation isachieved in that the contact structure is configured as a waveguide,wherein the ratio of the inductive to the capacitive coupling factor isequal to the product of the wave impedances of the individual waveguidesof the contact structure.

In an exemplary embodiment, the coupling structure has at least one, inparticular two, contact structures per measuring port.

In a preferred embodiment, the circuit board is a multi-layer board witha plurality of substrate layers, wherein the signal waveguide isconfigured on a first substrate layer of the multi-layer board and atleast one contact structure is configured on the first or at least oneother substrate layer of the multi-layer board.

As an example, at least two of the contact structures are arranged ondifferent substrate layers of the multi-layer board.

In a particularly preferable embodiment, the at least one contactstructure has contact points which are configured and arranged such thatcontacting with on-wafer or PCB test probes results in animpedance-controlled interface.

For rapid and simple calibration of the contactless measuring system,also arranged on the circuit board is at least one calibration element,which is connected to at least one signal waveguide on which at leastone contact structure is arranged such that the arrangement of thecontact structure on the signal waveguide of a calibration elementcorresponds to the arrangement of the contact structures on the signalwaveguides of the electrical circuit.

At least one calibration element is connected to a number of signalwaveguides which corresponds to the number of measuring ports of thecontactless measuring system.

In order to provide the calibration elements and the electrical circuitwith identical coupling conditions and optimum calibration, at least onecontact structure on the signal waveguides of the calibration elements,said contact structure being assigned to a measuring port of thecontactless measuring system, is configured identically to the at leastone contact structure on the signal waveguides of the electricalcircuit, said contact structure being assigned to said measuring port ofthe contactless measuring system.

With a calibration substrate of the aforementioned type it is provided,according to the invention, that the calibration substrate is configuredas a circuit board, on which at least one contact structure isconfigured and arranged such that this contact structure is galvanicallyseparated from the signal waveguide, forms part of the couplingstructure, is arranged completely within the near field of the signalwaveguide and has at least one contact point which is electricallycontactable with a contact of a test probe.

This brings the advantage that the contact structure and thus theoverall coupling structure has a precisely defined geometricalarrangement to the signal waveguide, wherein manual positioning of thecoupling structure can be dispensed with. Reproducible coupling betweenthe signal waveguide and the coupling structure is achieved by simplemeans.

The contactless measuring system is preferably configured as describedabove, wherein it is particularly preferable that at least one contactstructure on the signal waveguides of the calibration elements, saidcontact structure being assigned to a measuring port of the contactlessmeasuring system, is configured identically to the at least one contactstructure on the signal waveguides of the electrical circuit, saidcontact structure being assigned to said measuring port of thecontactless measuring system.

At least one calibration element is connected to a number of signalwaveguides which corresponds to the number of measuring ports of thecontactless measuring system.

Suitably, on the circuit board of the calibration substrate, at leastone electrical circuit is configured with at least one signal waveguideon which at least one contact structure is arranged such that thearrangement of the contact structure on the signal waveguide correspondsto the arrangement of the contact structures on the signal waveguides ofa calibration element.

In a preferred embodiment, at least one contact structure on the signalwaveguides of the calibration elements, said contact structure beingassigned to a measuring port of the contactless measuring system, isconfigured identically to the at least one contact structure on thecalibration substrate on the signal waveguides of the electricalcircuit, said contact structure being assigned to said measuring port ofthe contactless measuring system.

The invention will now be described in greater detail making referenceto the drawings, in which:

FIG. 1 shows a schematic block circuit diagram of a preferred embodimentof a contactless measuring system according to the invention with avector network analyser,

FIG. 2 shows a first preferred embodiment of a contact structure for thecontactless measuring system according to the invention,

FIG. 3 shows a second preferred embodiment of a contact structure forthe contactless measuring system according to the invention,

FIG. 4 shows a first preferred embodiment of a calibration substrateaccording to the invention for the contactless measuring systemaccording to the invention in plan view,

FIG. 5 shows an exemplary alternative embodiment of a contact structurefor the contactless measuring system according to the invention,

FIG. 6 shows a further exemplary alternative embodiment of a contactstructure for the contactless measuring system according to theinvention,

FIG. 7 shows a further exemplary alternative embodiment of a contactstructure for the contactless measuring system according to theinvention,

FIG. 8 shows a further exemplary alternative embodiment of a contactstructure for the contactless measuring system according to theinvention,

FIG. 9 shows a further exemplary alternative embodiment of a contactstructure for the contactless measuring system according to theinvention,

FIG. 10 shows a further exemplary alternative embodiment of a contactstructure for the contactless measuring system according to theinvention,

FIG. 11 shows a further exemplary alternative embodiment of a contactstructure for the contactless measuring system according to theinvention,

FIG. 12 shows a further exemplary alternative embodiment of a contactstructure for the contactless measuring system according to theinvention,

FIG. 13 shows a further exemplary alternative embodiment of a contactstructure for the contactless measuring system according to theinvention,

FIG. 14 shows a second preferred embodiment of a calibration substrateaccording to the invention for the contactless measuring systemaccording to the invention in plan view, and

FIG. 15 shows a third preferred embodiment of a calibration substrateaccording to the invention for the contactless measuring systemaccording to the invention in plan view.

The preferred embodiment of a contactless measuring system according tothe invention shown in FIG. 1 comprises a vector network analyser 10having a signal source 12, signal lines 14 and 16 and a contactstructure with four coupling waveguides 18, each of which has an innerconductor 20 and an outer conductor 22. The coupling waveguides 18 areconfigured as printed conductor tracks on a printed circuit board 24.Also arranged on this printed circuit board 24 is a signal waveguide 26configured as a printed conductor track. The signal waveguide 26 is partof an electronic circuit (not show in detail) provided on the printedcircuit board 24 with corresponding electronic components.

The coupling waveguides 18 together with a test probe 28 form a couplingstructure for the contactless measuring system in order to decouplecontactlessly an electromagnetic wave running along the signal waveguide26. The test probes 28 each create an electrical contact with a couplingwaveguide 18 on one side, and with the measuring ports 30, 32, 34, 36 ofthe vector network analyser 10 on the other side.

The coupling waveguides 18 can be shaped almost arbitrarily. It isparticularly advantageous for the coupling waveguides 18 to beconfigured in impedance-controlled manner, i.e. the characteristic waveimpedance values of the arrangement are known and are optimised for lowreflection. The advantage of an impedance-controlled contact structurelies therein that optimum directional damping and a port which isinsulated over a broad bandwidth can be achieved.

Two examples of an impedance-controlled coupling waveguide 18 of thistype are shown in FIGS. 2 and 3. The coupling waveguide 18 shown in FIG.2 comprises a U-shaped inner conductor 20 and an outer conductor 22. Theouter conductor 22 can be variously configured. Firstly, the outerconductor 22 can be closed, i.e. the outer conductor arms 38 and 40close at the coordinate z=0, as indicated in FIG. 2 with dashed linesand secondly, the ends of the outer conductor arms 38, 40 can beseparated along z. For example, the arms 38, 40 then end at thepositions +z₁ and −z₁ or, as shown in FIG. 2, at the positions +z₂ and−z₂. Through the arrangement of the outer conductor 22 relative to theinner conductor 20, the coupling waveguide 18 corresponds to a bentcoplanar waveguide. Different variants of this coupling waveguide 18 arepossible. A variant without corners is shown in FIG. 3. By way ofexample here, the outer conductor arms 38 and 40 are joined to oneanother at the position z=0.

A further advantage of the contact structure according to the inventionis that no through contacts to earth (rear-sided base metalizing of thecircuit board 24) are necessary. However, the possibility of connectingthe outer conductors 22 of the coupling waveguides 18 to earth withthrough contacts is not ruled out.

For decoupling energy from the signal waveguide 26 of a test object(DUT—Device Under Test) at least one contact structure or couplingwaveguide 18 is brought into the near field of the respective signalwaveguide 26. The coupling waveguide 18 can be situated on the samesubstrate as the respective signal waveguide 26, or in the case of amulti-layer board, on another substrate. The contact structure with thecoupling waveguides 18 is then connected, for example, to a commercialsymmetrical on-wafer or PCB test probe. The reference sign 42 in FIGS. 2and 3 denotes the contact positions of the contacts of test probes withthe contact structure or the respective coupling waveguide 18. In orderto characterise an N-port test object, at least N coupling waveguides 18situated within the near field of the N signal waveguides 26 are needed.FIG. 1 shows the example of a 2-port test object (in this case, a simpleconductor=DUT) with four coupling waveguides 18.

The geometry of the coupling waveguides 18 and of the test probes 28both influence the coupling factor of the arrangement. The test probes28 are connected to (vectorial) receivers of, for example, aconventional network analyser, as shown in FIG. 1.

The procedure for measuring test objects embedded within planar circuitswith the aid of at least one impedance-controlled contact structure orat least one non-impedance-controlled contact structure within planarcircuits will now be described.

The method is essentially based on the method of contactless vectornetwork analysis. The disadvantage of contactless vector networkanalysis is that the use of the method for achieving accurate measuredvalues is very heavily dependent on the positioning accuracy of thecontactless test probes. According to the invention, it is also providedthat printed contact structures are used in combination withconventional test probes, rather than a complex automatic positioningsystem in combination with completely contactless probes. All the signallines of the test objects and of the calibration elements which arenecessary for system error calibration, must be provided with at leastone coupling waveguide 18 (contact structure).

An example of a practical implementation of a calibration substrate withembedded test objects (DUT3, DUT4) making use of contact structures withprinted coupling waveguides 18 is shown in FIG. 4. For 2-portcalibration, the contact structure comprises two coupling waveguides 18for each signal waveguide 26, said coupling waveguides being configured,for example, according to the embodiment of FIG. 2. For N-portcalibration, a contact structure with at least N coupling waveguides 18per signal waveguide 26 is necessary. When using a diversity calibrationmethod, it is also useful to utilise a contact structure with more thanN coupling waveguides 18 per signal waveguide 26.

Due to the small dimensions of the coupling waveguides 18, for example,on-wafer or PCB test probes can be reproducibly positioned on theidentical coupling waveguides 18 of the individual calibration elements(LINE1, LINE2, LINE3, LINE4, OPEN, SHORT). Once the system has beencalibrated, the scattering parameters of, for example, embeddedcomponents can be determined. However, the signal lines of thecomponents must have the same properties (geometry, wave impedance,etc.) as those of the calibration elements. In addition, the samecontact structure must be present on the planar circuit at every signalwaveguide 26 of the embedded test object (DUT) as used for thecalibration.

The method therefore involves the placement of a contact structure, forexample, in the form of a coupling waveguide 18 within the near field ofthe signal waveguide 26 of the calibration and test objects on a circuitboard 24. The coupling waveguides 18 are arranged and configured on thecircuit board 24 such that they barely disrupt the function of a circuitand also can be connected to, for example, conventional on-wafer or PCBtest probes.

FIGS. 5 to 13 illustrate various exemplary embodiments of contactstructures 44. The contact structures 44 can have very particular forms.In principle, any desirable form can be used. In order to create areproducible coupling between the signal waveguide 26 and the couplingwaveguide 18 or the signal waveguide 26 and the test probe 28 or thesignal waveguide 26 and the coupling waveguide 18 and the test probe 28,the contact structure 44, if said contact structure comprises a materialsurface, either has holes in which the test probe is positioned, or hasa marked geometry on which the test probe is positioned. Alternatively,the contact structure 44 can also be configured as a notch in thesubstrate.

FIG. 14 shows a second preferred embodiment of a calibration substrateaccording to the invention which is configured on a circuit board 46.Parts with the same function are identified with the same referencenumbers as in FIGS. 1 and 4, so that reference is made to thedescription relating to FIGS. 1 and 4 above for their elucidation. Aplurality of calibration elements 48 is arranged on the calibrationsubstrate and each calibration element 48 is connected to one, two orthree signal waveguides 26. As distinct from the first embodimentaccording to FIG. 4, no coupling waveguides are provided on the signalwaveguides 26, but rather contact structures 44 as shown in FIGS. 5 to13. Signals are optionally fed to the signal waveguide 26 at suitablecontact sites 50. This calibration substrate comprises different 1-port,2-port and 3-port calibration standards 48 and different contactstructures 44.

FIG. 15 shows a third preferred embodiment of a calibration standardaccording to the invention, which is configured on a circuit board 46.Parts with the same function are identified with the same referencesigns as in FIGS. 1, 4 and 14, so that reference is made to thedescription relating to FIGS. 1, 4 and 14 above for their elucidation.In this embodiment, an electronic circuit 52 is also provided withcomponents 54 (DUTs) to be tested on the circuit board 46 of thecalibration substrate. Conversely, it can also be said that calibrationelements 48 are also arranged on the circuit board 46 with theelectronic circuit 52. The contact structure 44 for a particularmeasuring port on the signal waveguides 26 of the calibration elementsare configured identically to the contact structure 44 for thismeasuring port on the signal waveguides 26 of the electronic circuit 52.

For the correct measurement of the scattering parameters of an N-porttest object, the measuring system must be calibrated. Depending on thecalibration, M different N-port calibration standards (calibrationelements 48), which are known or only partially known, are needed. Forcalibration using M calibration standards, the geometry and the positionof the contact structure and of the signal waveguide 26 must beidentical for each measuring port, although it can be different betweenthe N measuring ports.

If, for example, the scattering parameters of a 2-port object are to bemeasured, then for an LLR calibration, three 2-port calibrationstandards are needed. These can be, for example, two lines of differentlength and two short-circuits, wherein the short-circuits each representa 1-port object, but together correspond to a 2-port object. The three2-port standards can comprise two different

1. Contactless measuring system comprising at least one test probe (28)forming part of a coupling structure for contactless decoupling of asignal running on a signal waveguide (26), wherein the signal waveguide(26) is configured as a conductor track and as part of an electriccircuit (52) on a circuit board (24) of the electrical circuit,characterised in that at least one contact structure (18; 44) isconfigured and arranged on the circuit board (24) such that this contactstructure (18; 44) is galvanically separated from the signal waveguide(26), forms part of the coupling structure, is arranged completelywithin the near field of the signal waveguide (26) and comprises atleast one contact point (42) which can be electrically contacted by acontact of a test probe (28).
 2. Contactless measuring system accordingto claim 1, characterised in that the contact structure is configured asa conductor track on the circuit board (24).
 3. Contactless measuringsystem according to one of the preceding claims, characterised in thatthe contact structure is configured so that said contact structure canbe contacted by a test probe (28) in impedance-controlled manner. 4.Contactless measuring system according to one of the preceding claims,characterised in that at least one contact structure is configured as acoupling waveguide (18) with an inner conductor (20) and an outerconductor (22).
 5. Contactless measuring system according to one of thepreceding claims, characterised in that at least one contact structure(44) is configured as at least one contact point or contact surface fora contact of a test probe (28).
 6. Contactless measuring systemaccording to one of the preceding claims, characterised in that thecontact structure (18; 44) and/or the signal waveguide (26) isconfigured as printed conductor tracks on the circuit board (24). 7.Contactless measuring system according to one of the preceding claims,characterised in that the circuit board (24) is configured as a printedcircuit board (PCB) or a wafer.
 8. Contactless measuring systemaccording to one of the preceding claims, characterised in that thecontact structure is configured as a waveguide, wherein the ratio of theinductive to the capacitive coupling factor is equal to the product ofthe wave impedances of the individual waveguides of the contactstructure.
 9. Contactless measuring system according to one of thepreceding claims, characterised in that the coupling structure has atleast one, in particular two, contact structures (18; 44) per measuringport.
 10. Contactless measuring system according to one of the precedingclaims, characterised in that the circuit board (24) is a multi-layerboard with a plurality of substrate layers, wherein the signal waveguide(26) is configured on a first substrate layer of the multi-layer boardand at least one contact structure (18; 44) is configured on the firstor at least one other substrate layer of the multi-layer board. 11.Contactless measuring system according to claim 10, characterised inthat at least two of the contact structures (18; 44) are arranged ondifferent substrate layers of the multi-layer board (24). 12.Contactless measuring system according to one of the preceding claims,characterised in that the at least one contact structure (18; 44) hascontact points (42) which are configured and arranged such thatcontacting with on-wafer or PCB test probes results in animpedance-controlled interface.
 13. Contactless measuring systemaccording to one of the preceding claims, characterised in that alsoarranged on the circuit board (24; 46) is at least one calibrationelement (48), which is connected to at least one signal waveguide (26)on which at least one contact structure (18; 44) is arranged such thatthe arrangement of the contact structure (18; 44) on the signalwaveguide (26) of a calibration element (48) corresponds to thearrangement of the contact structures (18; 44) on the signal waveguides(26) of the electrical circuit (52).
 14. Contactless measuring systemaccording to claim 13, characterised in that as the calibration element(48) a short-circuit standard, an open circuit standard, a resistancestandard and/or a conductor standard is provided on the circuit board(24; 46).
 15. Contactless measuring system according to claim 13 or 14,characterised in that at least one calibration element (48) is connectedto a number of signal waveguides (26) which corresponds to the number ofmeasuring ports of the contactless measuring system.
 16. Contactlessmeasuring system according to at least one of the claims 13 to 15,characterised in that at least one contact structure (18; 44) on thesignal waveguides (26) of the calibration elements (48), said contactstructure being assigned to a measuring port of the contactlessmeasuring system, is configured identically to the at least one contactstructure (18; 44) on the signal waveguides (26) of the electricalcircuit (52), said contact structure being assigned to said measuringport of the contactless measuring system.
 17. Calibration substrate fora contactless measuring system, comprising at least one test probe whichforms part of a coupling structure for contactless decoupling of asignal running on a signal waveguide (26), wherein at least onecalibration element (48), in particular a short-circuit standard, anopen circuit standard, a resistance standard, or a conductor standard isprovided on the calibration substrate, wherein the at least onecalibration element is electrically connected to at least one signalwaveguide (26), in particular a microstrip transmission line or acoplanar waveguide, characterised in that the calibration substrate isconfigured as a circuit board (46) on which at least one contactstructure (44) is configured and arranged such that said contactstructure (44) is galvanically separated from the signal waveguide (26),forms part of the coupling structure, is arranged completely within thenear field of the signal waveguide (26) and comprises at least onecontact point (42) which can be electrically contacted by a contact of atest probe (28).
 18. Calibration substrate according to claim 17,characterised in that the contactless measuring system is configuredaccording to at least one of the claims 1 to
 12. 19. Calibrationsubstrate according to claim 18, characterised in that at least onecontact structure (44) on the signal waveguides (26) of the calibrationelements (48), said contact structure being assigned to a measuring portof the contactless measuring system is configured identically to the atleast one contact structure (44) on the signal waveguides (26) of theelectrical circuit (52), said contact structure being assigned to saidmeasuring port of the contactless measuring system.
 20. Calibrationsubstrate according to at least one of the claims 17 to 19,characterised in that at least one calibration element (48) is connectedto a number of signal waveguides (26) which corresponds to the number ofmeasuring ports of the contactless measuring system.
 21. Calibrationsubstrate according to at least one of the claims 17 to 20,characterised in that at least one electrical circuit (52) having atleast one signal waveguide (26) is arranged on the circuit board (46) ofthe calibration substrate and at least one contact structure (44) isarranged on said signal waveguide such that the arrangement of thecontact structure (44) on the signal waveguide (26) of the electricalcircuit (52) corresponds to the arrangement of contact structures (44)on the signal waveguides (26) of a calibration element (44). 22.Calibration substrate according to claim 21, characterised in that atleast one contact structure (44) on the signal waveguides (26) of thecalibration elements (48), said contact structure being assigned to ameasuring port of the contactless measuring system, is configuredidentically to the at least one contact structure (44) on thecalibration substrate on the signal waveguides (26) of the electricalcircuit (52), said contact structure being assigned to said measuringport of the contactless measuring system.